Twilight zones discovered deep underground – and sceintists don't know what they are
Some of the Earth’s most “extreme features” have been discovered deep, deep underground, and scientists can’t work out what they are. The mysterious zones have the power to slow down seismic waves by up to 50 per cent, yet experts don’t know what they’re made of or what role they play. These strange black holes (figuratively speaking) are located w...